Many organs are grown using biological scaffolds taken from
humans, though some can be manufactured or taken from animals.

For something like a liver, you can use a liver or a piece of
liver that isn't suited for live donation, and put it through a
digestion process that gets rid of all the donor cells, but
leaves all of the connective tissue and the outlines of their
blood vessels untouched.

"We basically can lift this organ up, it feels like a liver, we
can hold it like a liver, it looks like a liver, but it has no
cells," Atala said. "All we are left with is the skeleton, if you
will, of the liver. All made up of collagen, a material that's in
our body."

Cell search

A "ghost" rat liver with all the living
cells removed.

What's needed next are cells from the patient to populate that
organ skeleton. Currently most lab-grown organs have been using
stem cells taken from bone marrow – but there's hope that this
could one day be replaced by adult stem cells or even something
easier to harvest like skin cells, which could be turned into
different kinds of cells using special chemicals.

Sources of a patient's stem cells, like their cord blood or
amniotic fluid from when they were born, could be saved for a
long time and may provide a source of any cell type they want,
once the science is perfected.

Once a patient's cells are grown up in the lab and turned into
the right kind of cell, they can be inserted into the organ to
attach to the biological scaffold. Many of the organs with lots
of blood vessels, like the liver and kidneys, require a two-step
process (at least). First, the patients own blood vessel cells
can be inserted and grown in the blood vessels, then the rest of
the organ can be seeded with their other cells.

Bioprinted organs

In his TED talk, Atala discussed the idea of
using a three-dimensional printer to print organs on demand. His
team modified a desktop printer and put cells in the cartridge.
In his lecture, he said it takes about seven hours to print a
kidney, putting down one layer of cells at a time. That's just a
prototype though.

His team has created bone and implanted it in an animal, he said.
They are currently working on more sophisticated printers, which
could print right on the patient, including
printed skin cells, an incredible technology that could
change how we treat burns forever.

He imagines a similar approach could use an MRI to non-invasively
analyze a person's organ, then send information through a
computer and design the organ for the patient.